As disclosed in, for example, patent documents 1 and 2, humidity sensors are known.
In the patent document 1, a pair of comb-shaped electrodes is formed on a surface of a substrate, and a frame member made from a foam material is arranged around the comb-shaped electrodes. The whole area inside the frame member is covered with a humidity-sensitive film. Further, a pad section as an external connection terminal is formed on the substrate outside the frame member.
In the patent document 2, a humidity detection section and a circuit section are formed on the same substrate. The humidity detection section includes a pair of detection electrodes and a humidity-sensitive film. The circuit section processes an output signal from the humidity detection section. The pair of detection electrodes face each other on the same surface of the substrate are spaced from each other. The humidity-sensitive film covers the detection electrodes and a gap between the detection electrodes. Further, a pad (not shown) of the circuit section is connected to a bonding wire, and a dam section is formed between the humidity detection section and the pad section (the circuit section) of the substrate.
By the way, the pad section is generally made from aluminum based on the cost front, for example. Therefore, there is a concern that the pad section will be corroded when the humidity sensor is used in humidified atmosphere. In the patent document 2, a protection gel section made from a water-resistant material covers the pad section and protects the pad section from corrosion.
However, the protection gel section has flowability yet when the protection gel section is applied. Then, a hardening process is performed so that the protection gel section can be fixed in a predetermined position. Therefore, when the protection gel section having the flowability is applied to the pad section, the protection gel section may flow and adhere to a surface of the humidity-sensitive film. In such a case, a property of the humidity-sensitive film may be changed so that humidity detection accuracy may be reduced.
In the patent document 1, adhesion of the protection gel section to the humidity-sensitive film is reduced by the dam section. In the patent document 2, the adhesion of the protection gel section to the humidity-sensitive film is reduced by the frame member.